Canon EF 16-35mm f/2.8 L III USM

Razor sharp wide open, a seriously awesome lens I was in the market for a used version II, having read older reviews at the time it came out. And at half the price of a version III, I was almost sold. But I kept seeing references to the lens being soft in the corners, especially shooting wide open at 2.8, which concerned me as I planned to use it in low light. I spoke with three photographers (two pros) who have had owned both and not only did they confirm the issues with the version II, they raved about the upgraded optics of the version III lens. One said it's worth every penny, rated it a 10 out of 10. I ultimately decided to buy the version III, knowing I would regret it if I didn't. After using now for two weeks, I can say it was the best decision. The image quality is simply spectacular, perfectly balanced contrast and color, razor sharp across the image even in low light at 2.8. The auto focus is quite impressive as well. If you don't plan to use 2.8, the 4.0 version may be your best option, equally good optics and more affordable. But if you plan to shoot in low light, and you need 2.8, don't hesitate on this decision. Once you see the image quality, you'll forget the price. Read full review

Quality, bright to edges. Foreseeable deformations. This lens delivers exactly what we should expect from this third generation Canon wide-angle zoom: high quality and strong performance all the way to the corners. My main use is for architecture and, as to be expected, the lens will have a rather strong fisheye effect at the widest zoom and barrell at the narrowest. The lines are very straight at about 24mm. All deformations are very continuous and easy to correct/photoshop after shooting. Great all-around piece of equipment.

Best improvement of a Canon Lens You just cannot get the kind of edge to edge sharpness wide open at f/2.8 on any other lens these days. This is pretty much it's sharpest wide open. Light, durable and, fast and delivers amazing imagery!